Problem: What do the following two equations represent? $4x-5y = -3$ $-20x+25y = 15$
Solution: Putting the first equation in $y = mx + b$ form gives: $4x-5y = -3$ $-5y = -4x-3$ $y = \dfrac{4}{5}x + \dfrac{3}{5}$ Putting the second equation in $y = mx + b$ form gives: $-20x+25y = 15$ $25y = 20x+15$ $y = \dfrac{4}{5}x + \dfrac{3}{5}$ The above equations turn into the same equation, so they represent equal lines.